High-definition video from space shows the extreme power of Hurricane Florence

Governors of those states have already declared states of emergency, as have the governors of Virginia and Maryland.

The National Weather Service has issued strong warnings to residents of the Carolinas and other mid-Atlantic states, saying the hurricane would be the "storm of a lifetime", bringing damaging winds, life-threatening storm surges, and "catastrophic flooding".

As of Tuesday, about 1.7 million people in North and SC and Virginia were under warnings to evacuate the coast, and hurricane watches and warnings extended across an area with about 5.4 million residents.

A satellite image shows Hurricane Florence looming in the Atlantic Ocean as the sun rises over the U.S. Florence is expected to bring tropical storm conditions to North Carolina and SC on Thursday and hurricane conditions on Friday.

Forecasters with the National Hurricane Center said that while Florence is expected to slow down considerably by late Thursday and into Friday, it will still be an "extremely unsafe major hurricane" when it makes landfall.

For many of those under evacuation orders, getting out of harm's way has proved difficult, as airlines canceled flights and motorists had a hard time finding gas.

Florence's winds in the afternoon were down slightly to 125 miles per hour (205 kph), from a high of 140 miles per hour, and the Category 4 storm fell to a Category 3.

"This is not going to be a glancing blow", warned Jeff Byard, an administrator with the Federal Emergency Management Agency. At 8 a.m. (1200 GMT) on Wednesday the storm was located about 530 miles (855 km) southeast of Cape Fear, North Carolina.

Tropical storm-force winds extended 175 miles (280 kilometers) from Florence's center, and hurricane-force winds reached out 70 miles (110 kilometers). Some 3,000 people died in the aftermath of that storm. "We are ready for the big one that is coming!" Unsure of what they would find when they return home, the couple went shopping for a recreational vehicle.

"I'm scared we'll get 30 inches or more of rain", said Carol Trojniar, 69, a longtime Wilmington resident and retired real estate agent who has never experienced a Category 4 hurricane. "If we try to leave, we'll just get stuck in the rain". She said it will become a "major flooding event".